Rare is the NFL player who leaves the game on his own terms, and with his health relatively in tact.

Such is the case for former Patriots safety Steve Gregory, who announced his retirement through his agent David Canter on Sunday afternoon.

It is with tremendous respect, appreciation and admiration for the game of football that I've decided to announce my retirement effective immediately. After entering the game as an undrafted free agent, I was fortunate enough to play twice as long as the average player. This past off season, my wife Rosanne and I were blessed to welcome a daughter, Aviana, and spending time with her has changed my life's perspective. It is my hope to continue in football as a coach and I look forward to what the future holds. I'm tremendously happy with my decision and being able to walk away from this great game both healthy and on my own terms. I would be remiss in announcing my retirement without thanking my great family, coaches, teammates, scouts, trainers, agent and all of the fans that have supported me along the way.

Gregory was signed by the Patriots in 2012 after five seasons with the San Diego Chargers. Perhaps the most memorable play of his time in New England was what's now commonly referred to as the "Butt Fumble," when he scooped up a Mark Sanchez fumble and ran it in for a score in a blowout win over the Jets two seasons ago.

But Gregory was a key member of the Patriots defense who contributed in campaigns that led to back-to-back AFC Championship game appearances. Last season, when the veteran core of the Patriots defense -- Jerod Mayo, Vince Wilfork and Tommy Kelly -- hit season-ending injured reserve, Gregory's role was magnified. After second-year linebacker Dont'a Hightower was given the opportunity to take Mayo's role as play-caller, the team deemed Gregory better suited for the job.

He missed two games with a thumb injury last season, but was a capable and knowledgeable defender on the back end of the Patriots defense.

It's fitting that Gregory plans to enter into the field of coaching now that he's through with his playing career. He was praised by teammates last year for his smarts on the field and in the meeting room.

“When we’re preparing for games, he’s not only able to watch film and see things coming, but he’s able to go to the coaches and say, ‘Why don’t we tweak this defense this way, because it better fits what they do?’ ” Devin McCourty said back in January. “When we’re in meetings we’ll have something in the defense and we’re watching and Steve will say, ‘Why don’t we do this?’ We’ll all sit there and look at him and be like, ‘You’re right, that probably would be better.’ I think that’s what makes him so good.

“Steve always has something each week we play that he sees and things we can do. That’s why we call him a future head coach.”

“Steve is a very instinctive player, not only smart but he has good anticipation and awareness of what’s happening back there. I think that’s definitely one of his strengths,” Belichick said. “He’s very instinctive in the running game and the passing game, formations. Yeah, we’re really fortunate.”

In 2013, Gregory finished the season with 79 tackles and a sack. He was also rated a top-25 safety by Pro Football Focus. He had 116 tackles and three interceptions in 26 games with the Patriots over two seasons, and for his career he finished with seven picks and 357 tackles.

He was released by the Patriots back in February and picked up by the Chiefs at the end of last month. Kansas City needed some safety depth after Sanders Commings went down with an ankle injury this summer, but there's no guarantee Gregory would have made the final 53-man roster.

Regardless, he didn't have to wait for the first round of cuts to know that his time as a player was over. He realized on his own that it was time to start a new chapter.

Based on the early reviews from his former teammates and head coach, he should have a coaching interview or two lined up before too long.

Phil Perry serves as a general reporter for Comcast SportsNet, mainly covering the New England Patriots. Follow Phil on Twitter here.